In general, a double clutch transmission having two input shafts is required to use a double clutch that includes two discs to transmit a power transmitted from an engine. The double clutch demands two clutches and operates in a dual gear manner. Thus, since the shaft having the dual structure changes whenever the gear is shifted to the next one up or down, a shift speed is quick, and the shaft change is of help to actual fuel efficiency.
Particularly, a dry double clutch transmits a power of an engine by using friction between a clutch disc and a pressure plate without using oil, unlike the conventional wet double clutch. The dry double clutch is disclosed in Korean Patent Registration No. 10-1180599.
According to the related art, a double clutch (1) includes a damper flywheel (3) and a set double clutch (5). The double clutch includes a first diaphragm spring (7) fixed to a co-axis so that an outer circumference of the first diaphragm spring is covered by an annular casing (13) of the set double clutch (5), and a portion except for the outer circumference is exposed to the outside of the annular casing (13), a cover plate (9) that is disposed adjacent to the co-axis inside the first diaphragm spring (7) to support the outer circumference of the first diaphragm spring (7) by an embossing part (15) that is disposed on the co-axis to protrude outwards from the outer circumference, a second diaphragm spring (11) disposed adjacent to the co-axis inside the cover plate (9) to press a first pressure plate (21) of the set double clutch (5), and an annular support member (10) coaxially disposed between the outer circumference of the cover plate (9) and the second diaphragm spring (11) to allow the second diaphragm spring (11) to be supported by the cover plate (9).
Thus, in the double clutch (1) according to the related art, the cover plate (9) may be supported by the support member (10), and the embossing part (15) may be disposed from a centre of the cover plate (9) towards an outer circumferential end, i.e., at a position that is farthest away outwards from the centre of the cover plate in a radius direction. Thus, the outer circumference of the first diaphragm spring (7), which is supported by the embossing part (15), may also be disposed at a position that is farther away from the centre towards the outer circumferential end. Also, the first diaphragm spring (7) may maximally increase in diameter while a distance from the outer circumferential end of the first diaphragm spring (7) to the portion of the outer circumference, which is supported by the embossing part (15), is constantly maintained. As a result, since a casing (13) is constantly maintained in inner diameter, but the first diaphragm spring (7) increases in diameter, the diaphragm spring may increase in repulsive force and decrease in stress to improve durability.
However, as described above, the double clutch according to the related art may cause a problem in which an axis centre between the clutch and the diaphragm spring is warped when the diaphragm spring is contracted and restored. This mismatch in concentricity may cause eccentric contact between the pressure plate and the disc, thereby involving uneven wear of the disc.